custom properties in mirrored sheetmetal part

WI Hello,

I have following problem:

I start with a left side of a sheetmetal and create a mirror part ( insert -> mirror part) with the option to  import the custom properties (fig 1).

That's all fine as long you have both parts open you get the custom properties to propagate. If you only open the mirror part without

the original then all the properties are missing. Now I can set solidworks to open referenced parts by default and I get the custom properties just fine as long

as the incontext relationship is not locked. If it is locked then i get none of the custom properties of the left side unless i unlock the link to the original.

My question, how do you use mirror sheetmetal parts and get all the custom/configuration specific properties to show up in the mirrored part with the
link to the original locked. Important is that i want the link is locked (i only unlock the link if the part has been changed).

I would welcome a best practise approach from people with solid sheemetal practise and experience.

fig 1

fig 2

SolidworksSheet Metal